It relates in general to long range ordered alloys of the transition metals V, Fe, Ni, and Co and more specifically to long range ordered alloys of the AB.sub.3 type.
Long range ordered alloys are like intermetallic compounds whose atoms are arranged in order below a critical ordering temperature, T.sub.C. The term "long range order" refers to alloys having ordered structure extending for a distance of more than about 100 atoms in a single domain. The principal advantage of long range ordered alloys is their strength and stability at high temperatures. At temperatures below T.sub.C the ordered structure of the alloy has the lowest free energy. An ordered alloy can experience temperatures below T.sub.C for indefinite periods without undergoing significant compositional or phase changes. Above T.sub.C however, the tensile strength of ordered alloys is substantially reduced due to the disordering effect. In the prior art the principal disadvantage associated with long range ordered alloys has been their extreme brittleness. As a result, long range ordered alloys had not been used as structural material for high temperature applications. One notable exception is the ductile long range ordered alloy described in commonly assigned U.S. Pat. No. 4,144,059, issued Mar. 13, 1979, in the name of Chain T. Liu and Henry Inouye entitled "Ductile Long Range Ordered Alloy with High Critical Ordering Temperature and Wrought Articles Fabricated Therefrom." The alloys described in U.S. Pat. No. 4,144,059 were Co-based alloys having the nominal composition V(Co,Fe).sub.3 or V(Co,Fe,Ni).sub.3 comprising by weight 22-23% V, 14-30% Fe and the remainder Co or Co and Ni with an electron density no greater than 7.85. With this electron density limitation, the alloy, which contained no more than 23% V and 30% Fe could contain no more than about 10% by weight Ni and no less than about 37% by weight Co. The alloys of U.S. Pat. No. 4,144,059 are expensive due to the high cost of the required cobalt. The alloys are also of limited utility for nuclear applications because of the high neutron absorption cross section resulting from the cobalt content. A ductile long range ordered alloy having lower neutron absorption cross sections would be very attractive for structural components such as fuel-cladding for fast and thermal reactors and for a first wall material in controlled thermonuclear reactors.